The present invention relates to a pump having a non-voluminous type impeller, and in particular relates to small-sizing of the pump.
Small-sizing of a pump enables the manufacturer thereof to reduce manufacturing costs, as well as other costs for transportation and installation thereof. It is also advantageous for a customer, i.e., a user of the pump, since it enables to reduce in an area of the place where the pump is set up, and also to reduce the costs for constructing a pump station. Accordingly, the requirement for small-sizing of the pump is important for both the manufacturer and customer. For achieving such the requirement, it is well known that increase in revolution number of an impeller is effective, i.e., bringing it to operate at high speed.
As other means, it is also considered to set up or establish an output angle of blades of the impeller to be large, for the small-sizing of the pump by reducing an outer diameter of the impeller, while still satisfying a total pump head and a delivery amount for the same specification, but without increase of the pump revolution number.
Further, a technology of this kind according to the conventional art is disclosed, for example, in Japanese Patent Laying-Open No. Hei 6-123298 (1994).
However, for obtaining such the small-sizing of the pump by increasing up the revolution number of the impeller, i.e., high speed of the impeller, it is necessary to design the shape of blades and the configuration of flow passages, so as to generate less cavitations in the pump (i.e., an improvement on the performances in relation with cavitations), and it is very difficult in practice to solve the problem therewith.
On the other hand, for obtaining small-sizing of the pump while keeping the pump revolution number at the same by setting up the outlet angle of blades to be large, while still satisfying the total head and the delivery amount for the same specification, there are the following problems. Namely, the load rises upper unit length of blades when the outlet angle thereof is made large, and there is a tendency that an unstable portion appears remarkably on the head curve due to separation and/or stalls in a region of low flow rate. In this unstable portion, since there exist two (2) or more operating points for the pump, the delivery amount is shifted between those points; therefore there is a problem that stable operation is impossible therein.
An object, therefore, according to the present invention, is to provide a pump which can be small-sized without the necessity of increasing the revolution number of the impeller, while suppressing the unstable portion from appearing on the head curve due to the separation and/or stalls within the region of low flow rate.
For achieving the above-mentioned object, according to the present invention, there is provided a pump, comprising: an impeller having blades; and a casing for storing said impeller therein, on an inner surface of which, confronting to said impeller, are formed plural numbers of grooves in a direction of pressure gradient of fluid, around a periphery thereof, for connecting between an inlet side of blades and an area on the inner surface of said casing where the blades exist, wherein, an outlet angle of the blade, being measured from a peripheral direction of the blade of said impeller, is set to be within a region from 30 degree to 90 degree.
Herein, according to the present invention, it is preferable in the pump as defined above, to set up said outlet angle of the blade within a region from 50 degree to 70 degree.
Further, according to the present invention, it is advantageous in the pump as defined above, to provide rear guide vanes in plural numbers thereof around a periphery of a hub which is provided the outlet side of said impeller, and to provide intermediate vanes on a surface of said hub, having a height being equal to or less than one-third (⅓) of that of the rear guide vanes, between said rear guide vanes.
And, according to the present invention, it is especially effective, when the pump as defined above is applied into a vertical shaft pump having a flow passage forming portion which is constructed with a pump casing and a delivery bent, and a pump shaft, which penetrates through said delivery bent vertically and is attached with the impeller at a lower side thereof.
In a case of applying the pump as defined above into the vertical shaft pump, it is possible to dispose plural numbers of bearings on said delivery bent in a vertical direction thereof, for supporting said pump shaft, and to construct an attachment portion of said impeller onto the pump shaft and said bearing at a lowest portion, so that a distance between them is larger than that between said bearing at the lowest portion and two (2) pieces of said bearings at a most upper portion.
Further, it is also possible to construct the pump as defined above, further comprising a hub provided at an outlet side of said impeller, and rear guide vanes provided on the hub, wherein said impeller, said hub, said rear guide vanes and said delivery bent are assembled together in one body as a hydraulic power portion, and being so constructed, that said hydraulic power portion can be assembled with or disassembled from the flow passage forming member which is constructed with the pump casing and the delivery bent, by inserting said hydraulic power portion into said flow passage forming member from above.
Another feature, according to the present invention, there is provided a pump, comprising: a casing; an impeller having plural numbers of blades, being provided within said casing; and plural numbers of grooves, which are provided on an inner surface of said casing, connecting between an inlet side of said impeller and an area on the inner surface of said casing where the blades exist, wherein, front guide vanes are provided in said casing at an upstream side of said impeller, and said front guide vanes are so set up, that a direction of absolute flow at an outlet of said impeller is directed into an axial direction of the pump at an amount of designed flow rate. In this manner, according to the present invention, it is preferable to set up the outlet angle of said blades at a value being equal or greater than 30 degree.
Another feature, according to the present invention, there is provided a pump comprising: a casing; an impeller having plural numbers of blades, being provided within said casing; and plural numbers of grooves, which are provided on an inner surface of said casing, connecting between an inlet side of said impeller and an area on the inner surface of said casing where the blades exist, wherein, said grooves are formed to be equal or greater than 5 mm in depth thereof, while to be smaller than the depth in width of said grooves; and an outlet angle of the blade is set to be within a region from 30 degree to 90 degree.
It is advantageous in the pump as defined above, to form said grooves being provided around a periphery of said casing in the plural number thereof, so that a total of the widths of said grooves is from about 30% to 50% with respect to a peripheral length on the inner surface of said casing, where said grooves exist, while the depth of said grooves is equal or greater than 2 mm, so as to be from about 0.5% to 1.6% of an inner diameter of said casing where said grooves exist.
Further, as another feature according to the present invention, there is provided a vertical shaft pump, comprising: a pump casing; an impeller having plural numbers of blades, being provided within said casing; a delivery bent disposed in a downstream side of said pump casing; a pump shaft, penetrating through said delivery bent vertically and being attached with the impeller at a lower side thereof; and plural numbers of grooves, which are provided on an inner surface of said casing, connecting between an inlet side of said impeller and an area on the inner surface of said casing where the blades exist, wherein said grooves are formed to be equal or greater than 5 mm in depth thereof, while to be smaller than the depth in width of said grooves; an outlet angle of the blade is set to be within a region from 30 degree to 90 degree; and said delivery bent is formed in an oval shape in cross-section thereof, in which difference between inner and outer diameters of a curvature is smaller than width of a flow passage therein, on a cross-section in vicinity of the curvature of said flow passage.
Herein, according to the present invention, in the vertical shaft pump as defined above, a shape on the cross-section of said delivery bent is a circular shape on the cross-section at an inlet side and an outlet side thereof. Also, according to the present invention, it is desirable in the vertical shaft pump as defined in the above, to set up width h of the flow passage in a curvature radial direction Rb of said bent tube to establish following relationship with respect to width W of the flow passage in a direction perpendicular to a plane of the curvature (a direction perpendicular to the radius direction Rb), in a cross-sectional shape of said delivery bent on a cross-section, in vicinity of a center of the curvature of the flow passage thereof W=(1.3xcx9c2.0)h. Furthermore, according to the present invention, it is advantageous in the vertical shaft pump as defined in the above, wherein cross-section area of the flow passage on a cross-section to set up said delivery bent in vicinity of a center of the curvature of the flow passage thereof to be as from 1.0 time to 1.2 times large as cross-section area at an inlet portion of said delivery bent. And, according to the present invention, also it is advantageous in the vertical shaft pump as defined above, to form plural numbers of grooves on an inner wall surface of said delivery bent in a direction of main flow therein.